The invention disclosed and claimed herein is generally directed to apparatus for conserving power in a medical diagnostic imaging system, such as a mobile X-ray unit. More particularly, the invention is directed to apparatus of such type for use with a medical diagnostic imaging system operated by power from an electric battery or other device having a limited power storage capacity.
As is well known, the term "medical diagnostic imaging system" is generally applied to equipment which uses a radiographic or magnetic technique to provide images of internal human body structures. Such equipment includes X-ray, computed tomography (CT) and magnetic resonance (MR) imaging systems, although it is not limited thereto. As is further well known, these types of systems are comparatively expensive. Accordingly, system suppliers are increasingly interested in developing diagnostic imaging equipment which is portable or mobile, so that it can be readily moved from one location of use to another. The utility of such equipment may thereby be significantly enhanced. Developments of this type are exemplified by a product of the General Electric Company, which is known as the AMX-4 X-ray unit. This product comprises an X-ray machine mounted on a wheeled carriage and provided with a drive motor and steering controls. The motor is powered by a rechargeable battery likewise mounted on the X-ray unit. The unit can thus be easily moved, for example, from one room to another in a hospital.
In mobile units of the above type, it has been found useful to employ the storage battery to operate respective X-ray imaging components, such as the generator, inverter and rotor controller, in addition to operating the unit drive motor. This arrangement minimizes components. Moreover, such arrangement enables the unit to be readily moved from one X-ray site to another, and then operated at the new site without concern about the availability of an external power source, such as an electric outlet of suitable voltage. However, the power storage capacity of a single battery is limited, and such dual use may tend to draw battery power down quickly under certain conditions. While the battery can be recharged when the X-ray unit is not in use, the needs of a health care environment are sometimes very unpredictable. For example, a series of medical emergencies could arise, requiring continuous use of the X-ray unit over an extended period of time, without opportunity to recharge the battery. If battery power was low at the beginning of the period, or if the unit consumed power unnecessarily, the battery might become depleted when power was still needed to acquire X-ray exposures of a patient. Thus, in such mobile X-ray and other diagnostic imaging equipment, it would be desirable to conserve or minimize use of battery power as much as possible. In some circumstances, it could be significantly beneficial to conserve even comparatively small amounts of power, if such conservation would enable the battery to acquire several additional X-ray exposures. It could also be desirable to minimize strain on the battery during recharging procedures.